The human nasal cavity extends from the nares to the choana. Extending from this space, which is roughly rectangular, are four sets of sinuses which are hollow spaces in the bone of the head. The sinuses extend above, below, medial to and posterior to the boney orbit. The nasal and sinus cavities are normally able to clear mucous produced in their linings through a transport system called the mucociliary blanket, a self-cleaning lining of the nose and sinuses. The mucous is transported out of the sinus openings which vary from 1 mm in diameter to 2 cm in diameter and, in some cases, can be even larger. Normally, the mucous is then cleared out of the nasal cavity into the nasopharynx and down into the pharynx where it is swallowed. The mucocilliary blanket clears out viruses, bacteria, fungi and other debris from the nose and sinuses so that they do not have the ability to cause infection, both locally and systemically.
Sinusitis is caused by obstruction to the sinus ostia, or a breakdown of the mucocilliary clearance. The obstruction is caused by mucosal edema from viruses, allergies or any other irritants in inspired air. With the sinus ostia obstructed, mucous produced in the sinus accumulates and provides a perfect medium in which bacteria can grow. If an infection occurs, this leads to pressure in the sinus with facial pressure/pain, nasal obstruction, thick purulent nasal and post-nasal discharge and generalized fatigue.
Conventionally, patients are treated for sinusitis with oral antibiotics, steroid nasal sprays, decongestants and, occasionally, oral steroids. Nasal irrigations are used as well and are effective in clearing debris from the nasal cavity but are very irritating to the Eustachian tubes and pharynx. If the sinusitis does not clear after maximal medical therapy, or if the infections recur frequently, then surgery must be considered to enlarge the openings to the sinuses. Once the sinus openings have been enlarged, the sinuses are more accessible but are still poorly accessible with currently available nasal/sinus irrigation units. Sometimes the surgery is performed only with the idea that it will render sinus irrigations more effective. Even after such surgery, and despite the availability of many different devices, accessing the sinuses with saline or medicated liquid to clear the infection is still very ineffective.
In an article by Peter Wormald et al entitled “A Comparative Study of Three Methods of Nasal Irrigation” (Laryngoscope. 2004 December; 114(12):2224-7), the available methods of nasal and sinus irrigation are detailed and compared. The three techniques described are: nebulization (rhinoflow); nasal irrigation (metered nasal spray); and nasal irrigation in the Moffit's position (nasal douching with the top of the head positioned on the floor).
Nebulized medications are ineffective in entering the sinuses in any reliable fashion. Nasal rinse bottles are often effective in clearing the nose, but the irrigant rarely enters the sinus in any significant way. Even if the irrigant or nebulized saline enters the sinus, the contact time is very transient and unpredictable, thereby significantly minimizing its effectiveness. One reason for this is that the orientation of the user's head during fluid application is preferably face-down to permit the liquid to have access to all of the intended cavities. However, when the face down position is assumed in these prior techniques, the liquid tends to quickly flow out of the nasal passages without sufficient residence time to be effective and without contacting the target areas. To compensate for this some prior techniques for irrigation of the nose and sinuses introduce excess liquid into the nasal passage, often causing users to experience Eustachian tube irritation with subsequent ear pain and the discomfort of fluid draining into their throats, making them cough and choke.
Most conventionally used methods of delivering medication systemically through the nasal cavity are inaccurate and ineffective because of the transient and unpredictable contact time between the medication and the target membrane.